Schulz said of Snoopy's character in a 1997 interview: "He has to retreat into his fanciful world in order to survive. Otherwise, he leads kind of a dull, miserable life. I don't envy dogs the lives they have to live."[3]

Snoopy has imagined himself as different things such as a pelican, a vulture, an author, and a World War One flying Ace. All of these have exactly the same formula: he pretends to be something, and fails: his extremely short "novels" are never published, he is consistently shot down by his imaginary enemy, and he can never be a convincing vulture, bear, or penguin, even to himself.

Snoopy appeared on the October 4, 1950 strip, two years after the first strip. On March 16, 1952,[4] his thoughts were first shown in a thought balloon. On June 28, 1957, Snoopy walked on his two hind legs like a human for the first time.

Snoopy's doghouse, originally depicted in a standard 3/4 view, was soon almost entirely depicted from the side later on.

He remained as a minor character until the 1970s.

He was depicted in the last strip that Charles Schulz ever wrote, on February 13, 2000.

Despite his history of conflicted loyalties and his occasionally disdainful attitude toward Charlie Brown (he can never remember Charlie Brown's name and thinks of him as "that round-headed kid"), Snoopy has shown himself steadfastly loyal to his current owner. He joined Charlie Brown in walking out of a game of Ha-Ha Herman when Peppermint Patty crudely insulted Charlie Brown (though she was unaware that Charlie Brown was within earshot). He also helped Charlie Brown recover his autographed baseball when a bully had taken it and was challenging Charlie Brown to fight him for it. When Charlie Brown has to stop dedicating himself to making Snoopy happy, Snoopy replies, "Don't worry about it. I was already happy."

Snoopy is usually depicted as having seven siblings, five of whom appear at some point in the strip: Andy, Belle, Marbles, Olaf, and Spike. Most often seen is Spike, who lives in the desert (near the real-life locale of Needles, California).

Some critics alleged that, after the strip's 1960s Golden Age, it suffered a decline in quality in the later years of its run; for example, in an essay published in the New York Press at the time of the final daily strip in January 2000, "Against Snoopy," Christopher Caldwell argued that the character of Snoopy, and the strip's increased focus on him in the 1970s, "went from being the strip's besetting artistic weakness to ruining it altogether". He criticized Snoopy's inability to talk:

“

Snoopy was never a full participant in the tangle of relationships that drove "Peanuts" in its Golden Age. He couldn't be: he doesn't talk (all his words appear in "thought bubbles"), and therefore he doesn't interact. He's there to be looked at.

”

He went on to say that Snoopy "was way too shallow for the strip as it developed in the 1960s, and the strips he featured in were anomalies. "

After giving some other explanations, he concludes his essay that "You can say of Schulz's genius what Sally, Peppermint Patty, Marcie and Franklin said of their homework on countless occasions through the decades: His Dog Ate It."[6]

Following the Apollo I fire, Snoopy became the official mascot of aerospace safety, testing and the rebuilding of the Apollo Program.

The Apollo 10lunar module was named Snoopy and the command moduleCharlie Brown. While not included in the official mission logo, Charlie Brown and Snoopy became semi-official mascots for the mission, as seen here[7] and here. Schulz also drew some special mission-related artwork for NASA , and several regular strips related to the mission; one showing Snoopy en route to the moon atop his doghouse with a fishbowl on his head for a helmet. The strip that ran on July 21, 1969 – one day after the Apollo 11 lunar module Eagle landed on the moon – included a full moon in the background, with a black mark on it representing the module.[1]

The Silver Snoopy award is a special NASA honor, in the form of a sterling silver pin with an engraving of Snoopy in a spacesuit helmet. It is given by an astronaut to someone who works in the space program that has gone above and beyond in pursuit of quality and safety.[8]

Snoopy is the name of a United States Air Force B-58 Hustler bomber, serial number 55-0665, which was modified to test a radar system.[9]

American insurance company MetLife has used Snoopy as their corporate mascot since the 1980s. Snoopy One, Snoopy Two and Snoopy J are three airships owned and operated by MetLife that provide aerial coverage of sporting events, and feature Snoopy as the World War I flying ace on their fuselage.[10]